POS0133 HIGH-RESOLUTION PERIPHERAL QUANTITATIVE COMPUTED TOMOGRAPHY FOR THE EVALUATION OF BONE EROSIONS OF METATARSOPHALANGEAL JOINTS IN RHEUMATOID ARTHRITIS: A PILOT STUDY
Authors: J. Meinhardsson, R. Klose-Jensen, J. Therkildsen, B. Langdahl, E. M. Hauge, K. Keller
Journal: Annals of the Rheumatic Diseases (2022)

Background Bone erosion in rheumatoid arthritis (RA) is most commonly detected in the wrist, metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints. High-resolution peripheral quantitative computed tomography (HR-pQCT) has successfully been used to quantify bone erosions in the wrist and MCP joints. A recent study highlights that HR-pQCT of only two MCP joints has equal accuracy to detect erosive disease in RA patients compared to conventional radiography (CR) of the hands, wrists, and feet (44 joints) 1 . However, no study has evaluated the MTP joints by HR-pQCT. Objectives To characterize the localization, size and frequency of erosions in the 4 th and 5 th MTP joints. Furthermore, to evaluate the sensitivity for the detection of erosion in the 4 th and 5 th MTP joints by HR-pQCT, compared to CR. Methods This single-centre cross-sectional study included 42 patients with established RA (disease duration ≥ 5 years). The right foot was imaged by HR-pQCT in a 2.7 cm long region corresponding to the 4 th and 5 th MTP joint. Blinded to patient data, the number and volume of bone erosions by HR-pQCT were measured and scored according to the SPECTRA criteria 2 . CR of 44 joints was evaluated according to the Sharp/van der Heijde (SHS) method. Results The patients (62% women) had a median disease duration of 12 years (interquartile range (IQR): 7 – 20). HR-pQCT of the 4 th and 5 th MTP joints identified erosions in 38 (90%) patients. The total erosion volume (V tot ) was 2610 mm 3 in all quadrants of the 4 th and 5 th MTP joints. Erosions were most frequently found at the lateral aspect of the 5 th metatarsal head (MH), including 1261 mm 3 (48%) of V tot (Figure 1). CR of 44 joints detected erosions in 30 (71%) patients with a median SHS erosion score of 9 (5 – 28). The sensitivity and specificity (95% CI) of classifying patients with erosive RA by HR-pQCT and CR is displayed in Table 1. McNemar’s χ 2 test showed a significantly higher sensitivity of patients classified as having erosive RA by HR-pQCT of the 4 th and 5 th MTP joints than by CR of 44 joints (4.6, p = 0.03). Table 1. Comparing CR and HR-pQCT for classifying patients as having erosive RA, and for identifying erosions in the 4 th and 5 th MTP joints. Sensitivity &amp; specificity of classifying patients with erosive RA by HR-pQCT when CR of the hands, wrist and feet was used as reference CRHands, wrists, and feet Erosive RA CRHands, wrists, and feetNon-erosive RA Total Sensitivity (95% CI) HR-pQCT4 th and 5 th MTP jointsErosive RA 27 11 38 90.0 (73.5 – 97.9) Specificity (95% CI) HR-pQCT 4 th and 5 th MTP joints Non-erosive RA 3 1 4 8.3 (0.2 – 38.5) Total 30 12 42 Sensitivity &amp; specificity of classifying patients with erosive RA by CR when HR-pQCT was used as reference HR-pQCT4 th and 5 th MTP jointsErosive RA HR-pQCT4 th and 5 th MTP jointsNon-erosive RA Total Sensitivity (95% CI) CRHands, wrists, and feetErosive RA 27 3 30 71.0 (54.1 – 84.6) Specificity (95% CI) CRHands, wrists, and feetNon-erosive RA 11 1 12 25.0 (0.6 – 80.6) Total 38 4 42 Conventional Radiography (CR), High-resolution peripheral Quantitative Computed Tomography (HR-pQCT), Metatarsophalangeal (MTP), Rheumatoid Arthritis (RA), Confidence Interval (CI). Conclusion This is the first study to evaluate erosions with HR-pQCT of the 4 th and 5 th MTP joints, including a comparison to CR. Erosions were frequent at the lateral aspect of the MTP joints, suggesting that mechanical and biomechanical demands may play a role in the development of erosions in the MTP joints. The superiority of HR-pQCT compared to CR for detecting erosions provide a basis for larger studies assessing bone changes in the MTP joints. References [1]Klose-Jensen, R. , et al. Diagnostic accuracy of high-resolution peripheral quantitative computed tomography and X-ray for classifying erosive rheumatoid arthritis. Rheumatology (Oxford ) (2021). [2]Barnabe, C. , et al. Definition for Rheumatoid Arthritis Erosions Imaged with High Resolution Peripheral Quantitative Computed Tomography and Interreader Reliability for Detection and Measurement. J Rheumatol 43 , 1935-1940 (2016). Disclosure of Interests Jørgen Meinhardsson: None declared, Rasmus Klose-Jensen: None declared, Josephine Therkildsen: None declared, Bente Langdahl Speakers bureau: UCB, Amgen, Eli Lilly, Gedeon-Richter, Gilead, Astellas, Consultant of: UCB, Amgen, Eli Lilly, Gedeon-Richter, Gilead, Astellas, Grant/research support from: Amgen and Novo Nordisk, Ellen-Margrethe Hauge Speakers bureau: AbbVie, Sanofi, Sobi, MSD, UCB, Consultant of: AbbVie, Sanofi, Sobi, MSD, UCB, Grant/research support from: Novo Nordic Foundation, Danish Rheumatism Association, Danish Regions Medicine Grants, Roche, Novartis, Kresten Keller: None declared